Not applicable.
This invention relates in general to antifriction bearings and more particularly to an antifriction bearing that, under power derived from within the bearing, produces signals that reflect conditions associated with the bearing.
The typical antifriction bearing has inner and outer races provided with opposed raceways and rolling elements which are located between the races where they roll along the raceways when the bearing is set in operation, thereby reducing friction to a minimum. The bearing contains a lubricant and its ends are closed by seals to exclude contaminants from the interior of the bearing and of course to retain the lubricant in that interior. A bearing usually fails for lack of lubrication or by reason of a defect in one of its raceways or rolling elements. But the raceways and rolling elements are totally obscured and cannot be inspected without disassembling the bearing. This, of course, requires removing the bearing from that on which it is installed, whether it be a rail car journal, a vehicle axle, or a mill roll, to name a few.
Even so, a defect in an antifriction bearing will usually manifest itself in a condition that may be detected externally of the bearing, although not necessarily through a visual inspection. Typically a rise in temperature denotes a lack of lubrication, or perhaps, even a seizure in which both races turn and the antifriction bearing in effect becomes an unlubricated sleeve bearing. Spalling or other defects in the raceways or rolling elements may produce excessive vibrations in the bearing.
To be sure, devices exist for monitoring the operation of bearings. For example, railroads have trackside infrared sensors which monitor the journal bearings of passing trains, but they exist at a relatively few locations often many miles apart and will not detect the onset of a temperature rise occurring between such locations. Some bearings come equipped with their own sensors which are coupled to monitoring devices through wires. As a consequence, the race which carries the sensor for such a bearing must remain fixed, that is to say, prevented from rotating, lest the wires will sever. And with a railroad journal bearing, at least, the outer race preferably should remain free enough to xe2x80x9ccreepxe2x80x9d, that is rotate in small increments, so that wear is distributed evenly over the circumference of the outer raceway. Furthermore, preventing cup creep requires a costly locking mechanism.
The preferred embodiment of the present invention resides in an antifriction bearing having inner and outer races and rolling elements between the races. The bearing also includes a wireless self-powered sensor unit having one or more sensors in communication with a radio transmitter located within the confines of the bearing. The radio transmitter transmits signals generated by an appropriate sensor that reflect certain operating conditions of the bearing, and the transmitter derives the electrical energy required to operate it from a power supply that is also located within the confines of the bearing.